Sanity check - where to stash money for short term (6 years)?

I've got $140k I want to stuff into my kids' 529 accounts. However 529 accounts count against gifting limits, and purely for laziness I don't want to dip into the lifetime exemption (because I don't feel like filling out the forms come tax time). That means I can't drop $70k each into the accounts right now. So instead I'm putting in $10k/year, to allow for leeway on the $14k limit (for birthday money and such). But that means I need to have at least the full $20k available to each year over the next 6 years (already taken care of the $10k for this year).

I know not to put this in the market, since I need the principal to be available and don't want to pull money from elsewhere to make up downturns. It's currently sitting in a credit union savings account making 0.34%. I've thought of a couple of options, but I'm not sure if I'm missing others:

1. Build up a CD ladder with my CU. The 5-year rate is 1.85% right now, and mathwise I'd do better setting up 6 5-year CDs and break one each year than I would setting up a 1-year, a 2-year, etc. Early withdrawal penalty is 180 days of interest, no other fees.
2. Put it all into an Ally high yield online savings account at 0.99%. Are there any other catches to that besides the monthly transaction limit? I'm okay with only 6 transactions per month, since once the money goes in it will only come out once a year. But if there are other requirements like setting up paycheck direct deposit or making minimum monthly deposits or minimum monthly transactions, that's not going to work
3. Do a hybrid of Ally for the first 2 years of payments and a CD ladder for years 3-6, dumping the last year into the Ally account once its 5-year CD is up. 1- and 2-year rates on CDs are abysmal, but the 3-year is 1.35% and thus a better deal for years 3-6 than Ally. However taking the 1.85% 5-year and breaking it at the 1-year mark should net around 0.94-ish% vs. Ally's 0.99%, so I don't know if it's worth jumping through the hoops for that last 0.05%? That's $5 on $10,000 principal.

What else is out there? I don't expect to make any significant gains on this money until it makes its way into the 529s, but I'd like to negate as much inflation as possible.

Pre-emptive "You should read 'I have $X, what should I do with it'" rebuttal: This is a life insurance money. It's extra, non-essential, not part of my budget, and unneeded for standard advice (401k is maxed, IRA is maxed, emergency fund is in place, debts are paid, etc). As far as I'm concerned, this is money that should go to my children, except that I was the sole beneficiary so instead of it being theirs outright I have to gift it to them. Thus the dilemma. Otherwise I'd just dump $70k lump sum into each 529 and be done with it. It's also not the full amount of the life insurance, so "keep some for yourself" advice is already being followed.

Edit: One other thing I forgot. There is the option to do a lump sum into the 529 and spread that out over 5 years, which would allow me to get $70k in as a lump. But I've already contributed $2500 to one kid's 529 (the other's is brand new) this year, and I want to have room for birthday money (I like to put $1,000 into their accounts on their birthdays), which the five year election wouldn't leave room for.